Wireless Doorbell – Part 1

My new house currently has no doorbell and, whilst I could just buy a normal dumb wireless doorbell or install a wired doorbell, the temptation of making my own flexible system is too great. The majority of the sensors in the house communicate over MQTT, so this seemed the natural protocol to use for this project. Part one will focus on the creation of the bell push and the second part on the chime.

As the bell push will be powered from 2x AAA batteries, maximum power savings will be important. Therefore the ESP8266 will spend almost all of its time in deep sleep. Pressing the button will ground the reset pin and start at the beginning of the sketch. This will cause the ESP8266 to connect to the WiFi using a pre-defined IP address to save time, send an “ON” and battery level message to the MQTT broker, flash an LED for visual feedback for the person pushing the bell, and then go back to sleep. This circuit relies on the fact that the ESP8266 is capable of running down to about 2.2 volts, as a result a voltage regulator can be omitted which in turn avoids the issue of quiescent current which would shorten the battery life. The two capacitors across the power rails are there to handle that current spikes drawn by the ESP8266 when transmitting over WiFi.